x1 (predicate, relation, function, set of n-tuples) is the converse/conversion/complement/transpose/commutation/functional-'permutation' of x2 (same typing as x1), as defined on set/object/space/graph x4, with argument/input slots permuted via function/operator/marker/permutation/(group) action x3.
Members of the SE* series of Lojban cmavo can be supplied to x3, in addition to specification of other permutations which apply via group action.